The study focuses on studying the variance crosstalk standard deviation in a closed formula for Self-Phase Modulation (SPM) and Cross-Phase Modulation (XPM), which are very important nonlinear phenomena which affect the system performance. This is used to analyze the best performance with minimum crosstalk in Wavelength Division Multiplexing (WDM) systems and the direct effect of increasing the input signal power in the system with respect to the bit rate, channel spacing, pulse shape, modulation formula and the multi-pumping Distributed Raman Amplifier (DRA) (forward, backward and bi-directional) in the C-band.